1. Field of the Invention
The invention relates to windproof umbrellas and more particularly to a light windproof umbrella.
2. Description of Related Art
Umbrellas are widely used personal articles. It is often that wind will catch an umbrella user unaware and exert a force against an inner surface of a canopy of the umbrella so as to cause the canopy to invert from its normal operable position to an upward convex position.
Windproof umbrellas are thus developed for windy weather. For example, U.S. Pat. No. 7,980,262 discloses a windproof umbrella comprising a center post 10 comprising an upper grommet 11, an intermediate fixed ring 12, and a lower sliding runner 13; a plurality of ribs 20 each having one end 21 pivotably secured to the grommet 11 and another open end 22; a plurality of main joints 51 each formed at a portion of the rib 20 proximate to the other end 22; a plurality of stretchers 30 each having one end 31 pivotably secured to the ring 12 and the other end 32 slidably and pivotally secured to the main joint 51; a plurality of auxiliary joints 61 each formed at a portion of the stretcher 30; and a plurality of struts 40 each having an one end 41 pivotably secured to the runner 13 and another end 42 moveably secured to the auxiliary joint 61; a lower canopy 70 fastened in covering relationship on the ribs 20; and an upper canopy 80 having a center secured to the grommet 11 and an outer peripheral edge positioned over a portion of the lower canopy 70 in covering relationship to all of the main joints 51, wherein wind caught beneath the canopies 70, 80 applies pressure to the canopies 70, 80 to cause a portion of the upper canopy 80 to lift away from a portion of the lower canopy 70 to form a plurality pairs of communicating inner and outer vent holes 71, 81 with the other ends 32 of the stretchers 30 sliding away from the center post 10, each pair of the inner and outer vent holes 71, 81 being defined by the portions of the upper and lower canopies 70, 80, the adjacent ribs 20, and the adjacent main joints 51.
However, a number of drawbacks have been found in the prior art windproof umbrella. In detail, diameters of the stretchers 30, the struts 40 and the ribs 20 are required to be equal so that the umbrella can withstand the force exerted thereon by strong wind. This inevitably can increase the weight of the umbrella greatly, resulting in a decrease of portability of the umbrella. Further, a person has to exert a great force to grasp the center post 10 in windy weather. This can quickly exhaust the strength of the person holding the umbrella. Thus, the need for improvement still exists.